I've been using AtlasLoot Enhanced a long time, probably a year by now.
I have noticed that lately I've been having high addon memory usage, and AtlasLoot is on top of that list every time, with about 5-7 MiB usage.

AtlasLoot has a huge database, there is not a lot to be done (though I am cleaning things up where possible).

AtlasLoot itself should not be taking that much by itself, although that figure sounds about right for Atlasloot + all the data modules. Note that you can always disable data modules you don't use (like the pre-60 instances for example) to save memory.

These are the stats for the latest build of AtlasLoot. Note the main area where improvements can be made is the core 'AtlasLoot' mod, but even that is only 5-10%. The stats were derived from the !Profiler mod.